Polysiloxane-forming reactions of the above sort are disclosed, for example, in the "J. Polymer Sci." 54, 375 (1961) and U.K. Patent Specification No. 794,119.
For the preparation of quaternary phosphonium hydroxides, it has been known to react tetra-n-butylphosphonium iodide with silver oxide in an aqueous medium as shown by the following reaction formula (B) (see, U.K. Patent Specification No. 794,119 and U.S. Pat. No. 2,883,366). EQU (n-Bu).sub.4 PI+1/2Ag.sub.2 O+1/2H.sub.2 O.fwdarw.(n-Bu).sub.4 POH+AgI (B)
wherein n-Bu means a n-butyl group.
The above-described conventional process making use of silver oxide resulted in a very high production cost due to the high price of the silver oxide reagent and was hence not a satisfactory synthetic process from the industrial viewpoint. In addition, the reaction of the above conventional process was not a practical reaction in view of its low reactivity except for the use of the iodide as the halide, because the reaction velocity is extremely slow when the bromide or chloride is used as the halide.